The two main types of antennas are Omni-directional and directional. Omni-directional antennas radiate RF signal in a 360 degrees pattern and directional antennas emit the RF signal in a focused beam similar to the headlight of a car. If your application is a point to point WiFi link like from one building to another you would use a Directional antenna. If you need to send the WiFi signal 360 degrees then you would use and Omni directional antenna. If you have a point to multi point application, such as a campus environment then you would use a combination of Omni directional and Directional antennas.

A High Gain WiFi Antenna is a directional antenna (such as a Yagi antenna or parabolic grid antenna, etc.) that has a narrow radio wave beam width. In addition to using a directional, narrow beam width, a high gain WiFi antenna typically features gain of 12-14dBi and greater. By coupling the higher gain with the narrow, focused beam, long distance WiFi communications can be achieved.